Steam service just got an injection of Interplay titles, with a host of new games currently available for download. There's the classic Fallout games, which include Fallout, Fallout 2 and Fallout Tactics (available individually for $8.99 or as a bundle for $20), but also Kingpin ($8.99) and Sacrifice ($8.99), the former being a bloody FPS and the latter being an inventive combat-focused RTS. If you've got a PC, we'd suggest you at least check out the original Fallout. There's a demo you can grab from CNET right here.
[Update: Shagittarius reminds us that you can get Fallout games (not to mention Sacrifice and Kingpin) from GoG with no DRM for a few bucks less than Steam.]